A thin wire electrode travels continuously from a spool through guides above and below the workpiece, and discharges erode material as the wire passes through, cutting a slot along a programmed path. The wire never contacts the part and is discarded after a single pass, since it erodes as it works. The result is a profile cut through the full thickness of the material.

Cut hardened material without difficulty, produce internal corners far sharper than any cutter radius allows, cut delicate and thin sections without deflection because there is no cutting force, and cut tapers and different top and bottom profiles. It also cuts stacked plates in one pass and can separate features from solid material without access for a tool.

Because the wire must pass through the material to begin an enclosed cut. For a profile that starts at the edge of the plate the wire can be threaded from outside, but any internal aperture requires a hole through which the wire can be threaded first. That hole is usually produced by small-hole EDM drilling, which is why the two processes are so often found together in a toolroom.

Producing angled walls, which is essential in die making where a blanking or extrusion die needs relief below the cutting land so that slugs and profiles clear without binding. By moving the upper guide independently of the lower one, the machine can cut a constant taper, or even a different profile top and bottom, which is how complex die geometry is produced in one operation.

Wire is the largest, since it is consumed continuously and discarded after one pass, and consumption is proportional to cutting time rather than to material removed. Beyond that, deionising resin and filters need regular replacement to maintain water quality, and guides and power feed contacts wear. Running costs are predictable and should be included when comparing wire EDM against alternative processes.

The first pass cuts through at high energy for speed, and leaves a surface and size that reflect that. Subsequent skim passes at progressively lower energy remove very little material but improve surface finish, reduce the recast layer and bring the profile to final size. Accurate die work typically uses several passes, and the number is a direct trade between cycle time and final quality.

Water quality above all: conductivity is controlled by deionising resin, and drifting conductivity destabilises the discharge. Flushing must reach the cut, which becomes harder in thick sections and where the part geometry blocks the nozzles. Wire tension and guide condition affect straightness and accuracy. Material with internal stress can also close on the wire as it is cut, pinching it and causing breaks.